What is the likelihood that the B path is completed in under 15 days?

Thai Construction
A construction firm from the Phuket Province of Thailand has a five activity project lined up for the coming month. They have had some difficulty getting firm estimates on the activity durations and have resorted to the three time estimates approach to plan the project. The activities and optimistic, most likely, and pessimistic estimates (in days) for each are shown in the table.

Activity Predecessor Optimistic Most Likely Pessimistic
A - 5 7 10
B - 11 15 18
C A 8 12 15
D - 9 11 12
E D 6 8 10

A) 0.56
B) 0.27
C) 0.43
D) 0.16

Answer: A